Grade 10
  1. Mechanics  1.1. Dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration  1.1.6. Graphical representation of motion  1.1.7. Equations of motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Projectile motion  1.1.10. Relative speed  1.2. Dynamics  1.2.1. Newton's Laws of Motion  1.2.2. Inertia and mass  1.2.3. Force and its types  1.2.4. action and reaction force  1.2.5. Friction and its effects  1.2.6. Coefficient of friction  1.2.7. Circular motion  1.2.8. Centripetal force and centripetal acceleration  1.2.9. Momentum and Impulse  1.2.10. Conservation of momentum  1.2.11. Newton's third law and applications  1.3. Work, Energy and Power  1.3.1. Work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy  1.3.5. Mechanical energy  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.3.8. Renewable and non-renewable energy sources  1.4. Gravitational force  1.4.1. Newton's law of universal gravitation  1.4.2. Gravitational field and field strength  1.4.3. Acceleration due to gravity on different planets  1.4.4. Kepler's laws of planetary motion  1.4.5. Orbits and satellites  1.4.6. Weight and apparent weight  1.4.7. Gravitational potential energy
  2. Properties of matter  2.1. States of matter  2.1.1. Solid, liquid and gas  2.1.2. Molecular structure of matter  2.1.3. Intermolecular forces  2.1.4. Plasma and Bose–Einstein condensate  2.2. Pressure  2.2.1. Definition of Pressure  2.2.2. Pressure in liquids  2.2.3. Atmospheric pressure  2.2.4. Pascal's principle  2.2.5. Archimedes' Principle and Buoyancy  2.2.6. Surface tension and capillarity  2.3. Elasticity  2.3.1. Hooke's law  2.3.2. Stress and strain  2.3.3. Elastic Limit and Modulus of Elasticity  2.3.4. Applications of Elasticity
  3. Thermal physics  3.1. heat and temperature  3.1.1. Difference Between Heat and Temperature  3.1.2. Temperature scale  3.1.3. Thermal expansion  3.1.4. Thermal equilibrium  3.2. Heat transfer  3.2.1. Conductivity  3.2.2. Convection  3.2.3. Radiation  3.2.4. Insulation and its applications  3.3. Thermal properties of matter  3.3.1. Specific heat capacity  3.3.2. Latent heat and phase change  3.3.3. Boiling and Melting Point  3.3.4. Heat engines and refrigeration  3.4. Laws of Thermodynamics  3.4.1. Zeroth law of thermodynamics  3.4.2. First law of thermodynamics  3.4.3. Second law of thermodynamics  3.4.4. Carnot cycle
  4. Waves and optics  4.1. Nature and properties of waves  4.1.1. Types of waves in nature and properties of waves  4.1.2. Transverse and longitudinal waves  4.1.3. Wave parameters  4.1.4. Reflection and refraction of waves  4.1.5. Superposition and Interference  4.1.6. Standing Waves and Resonance  4.1.7. Doppler effect  4.2. Sound waves  4.2.1. Characteristics of sound waves  4.2.2. Speed of sound in different mediums  4.2.3. Applications of sound waves  4.2.4. Ultrasound and its uses  4.3. Light Waves and Optics  4.3.1. Nature of light  4.3.2. Reflection of light  4.3.3. Laws of reflection  4.3.4. Mirrors and Image Formation  4.3.5. Refraction of light  4.3.6. Snell's Law  4.3.7. Lenses and Image Formation  4.3.8. Total internal reflection and critical angle  4.3.9. Optical fibre  4.4. Optical Instruments  4.4.1. Microscope  4.4.2. Telescope  4.4.3. Human eye and vision defects  4.4.4. Camera and its working principle
  5. Electricity and Magnetism  5.1. Electrostatics  5.1.1. Electric charge and its properties  5.1.2. Conductors and Insulators  5.1.3. Coulomb's law  5.1.4. Electric field and field lines  5.1.5. Electric potential and potential difference  5.1.6. Capacitors and Capacitance  5.2. Current Electricity  5.2.1. Electric current and its measurement  5.2.2. Ohm's law  5.2.3. Resistance and resistivity  5.2.4. Series and Parallel Circuits  5.2.5. Electric power and energy  5.2.6. Kirchhoff's Laws  5.3. Magnetism and Electromagnetism  5.3.1. Magnetic field and field lines  5.3.2. Magnetic effects of electric current  5.3.3. Electromagnetic induction  5.3.4. Faraday's laws of electromagnetic induction  5.3.5. Transformers and Applications  5.3.6. AC and DC current
  6. Modern Physics  6.1. Nuclear physics  6.1.1. Structure of the atom  6.1.2. Bohr's atomic model  6.1.3. Electron Energy Levels  6.1.4. X-rays and applications  6.2. Radioactivity  6.2.1. Types of radiation  6.2.2. Half-life and radioactive decay  6.2.3. Nuclear reactions and applications  6.2.4. Fission and Fusion  6.3. Quantum physics  6.3.1. Wave–particle duality  6.3.2. Photoelectric effect  6.3.3. Energy quantization  6.3.4. Heisenberg's uncertainty principle
  7. Electronics and Communication  7.1. Semiconductors  7.1.1. Conductors, Insulators and Semiconductors  7.1.2. Diodes and their applications  7.1.3. Transistors and Logic Gates  7.1.4. LEDs and photodiodes  7.2. Communication Systems  7.2.1. Basics of communication  7.2.2. Analog and digital signals  7.2.3. Wireless and optical fibre communication  7.2.4. Radio Waves and Modulation

Grade 10 → Waves and optics → Sound waves ↓


Characteristics of sound waves


Sound waves are fascinating phenomena that play a vital role in how we experience the world. They are a type of mechanical wave that occurs when a vibrating source creates disturbances in a medium such as air, water, or a solid. These disturbances travel through the medium as waves and are then interpreted by our ears and brain as sound. In this lesson, we will explore the various characteristics of sound waves, including their frequency, wavelength, amplitude, speed, and more.

Frequency and pitch

One of the primary characteristics of sound waves is frequency. Frequency refers to the number of wave cycles that pass a point in a given time period, usually measured in hertz (Hz), where one hertz equals one cycle per second. The frequency of a sound wave is directly related to the pitch of the sound. High frequency waves produce high pitched sounds, while low frequency waves produce low pitched sounds.

For example, imagine a flute and a bass guitar. The flute produces high-frequency waves, resulting in a high-pitched sound. In contrast, the bass guitar produces low-frequency waves, resulting in a low-pitched sound. Different musical instruments produce sounds of different frequencies, allowing us to perceive a range of pitches.

low frequency high frequency

Wavelength

Wavelength is the distance between successive crests (or troughs) of a wave. It is usually represented by the Greek letter lambda (λ) and is usually measured in meters. The relationship between frequency (f) and wavelength (λ) can be expressed by the following formula:

λ = v / f

Here, v is the speed of sound in the given medium. From this formula, you can see that the wavelength is inversely proportional to the frequency; as the frequency increases, the wavelength decreases.

Amplitude and loudness

The amplitude of a sound wave refers to the height of the wave peak or the depth of the trough from its resting position. It is a measure of how much energy the wave carries. The larger the amplitude, the louder the sound is heard by our ears, and vice versa.

For example, a whisper has a lower amplitude than a shout. This is why a shout sounds louder than a whisper.

Speed of sound

The speed of sound is another important characteristic. It depends on the medium through which the sound wave travels. In dry air at 20°C, the speed of sound is about 343 meters per second (m/s). The speed of sound in solids and liquids is faster than in gases because the particles in solids and liquids are closer together, causing the wave to propagate more quickly.

For example, sound travels faster through water than it does through air. This is why sounds underwater reach your ears more quickly than sounds traveling through the air.

Sound intensity and decibels

Sound intensity is the sound power per unit area. The unit for measuring sound intensity is the decibel (dB). The decibel scale is logarithmic, meaning that an increase of 10 dB represents a tenfold increase in sound intensity.

For example, a normal conversation may have an intensity of around 60 dB, whereas a loud rock concert may be as loud as 120 dB or more, making it necessary to wear ear protection to prevent hearing damage.

Reflection, diffraction and refraction

Sound waves can also exhibit properties such as reflection, diffraction, and refraction.

  • Reflection: Sound waves reflect off surfaces just like light waves. This is why we hear echoes. For example, when you yell towards a rock, the sound waves bounce back, causing you to hear an echo.
  • Diffraction: Diffraction occurs when sound waves bend around obstacles or spread out after passing through small holes. This property explains why you can hear someone calling around a corner.
  • Refraction: Refraction means the change in the direction of sound waves when they travel from one medium to another. Sound waves travel at different speeds in different mediums, causing a bend. For example, sound waves traveling from air to water will change direction because their speed increases in water.
reflection: diffraction: refraction:

Doppler effect

Another interesting phenomenon associated with sound waves is the Doppler effect, which occurs when the source of a sound is moving relative to the observer. This changes the observed frequency of the sound.

A common example of the Doppler effect is the change in pitch of a passing ambulance siren. As the ambulance approaches, the sound waves are compressed, making the pitch higher. As it moves away, the sound waves are stretched, making the pitch lower.

The formula to calculate the observed frequency (f') when the source is moving towards the observer is:

f' = (v + v0) / (v - vs) * f

Where:

  • f' = observed frequency
  • v = speed of sound in the medium
  • v0 = speed of the observer
  • vs = speed of the source
  • f = actual frequency of the source

Applications of sound waves

Sound waves are used in various fields such as medicine, engineering and entertainment. Let's take a look at some examples.

  • Medical ultrasonography: High-frequency sound waves are used to create images of internal organs and tissues. This technique is widely used in prenatal scanning.
  • Sonar: Used by submarines and ships to detect underwater objects by sending out sound waves and detecting the reflected waves.
  • Music and recording: Sound waves are important in the recording and playback of music and other audio. Microphones convert sound waves into electrical signals, and speakers do the opposite.

Understanding these characteristics and phenomena gives us a complete understanding of the complexities of sound and its various roles in our daily lives.


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Characteristics of sound waves

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